Adjust Crt Grid Bias; Adjust Astigmatism; Adjust Trace Alignment; Adjust Geometry - Tektronix 2235A Instruction Manual

Adjustment Procedure
-
2235A Instruction
Remove the crt cover and connect a dc voltmeter
capable of measuring at least -2500V between pin2
of the crt socket and chassis ground. Pin 2 of the crt
is negative with respect to the chassis.
CHECK-Voltmeter reading is between -1 900V and
-21 00
v.
Disconnect the voltmeter leads and replace the crt
cap and cover.
Adjust CRT Grid Bias (R851)
Connect a 50-0 termination to the EXT Z AXlS
INPUT connector located on the rear panel.
Adjust the front-panel FOCUS control to produce a
well-defined dot.
Rotate the A INTENSITY control fully counter-
clockwise.
ADJUST-Grid Bias (R851) for a visible dot. Then
back off the Grid Bias potentiometer until the dot just
disappears.
Disconnect the 50-0 termination from the EXT Z
AXlS INPUT connector.
Adjust Astigmatism (R874)
Set:
A INTENSITY Visible display
CH 1 VOLTSIDIV
5 mV
Channel 1 Input Coupling DC
A SECIDIV
5 I*S
Connect the leveled sine-wave generator output via
a 50-0 cable and a 50-0 termination to the CH 1
input connector.
Set the generator to produce a 50-kHz, 4-division
display.
ADJUST-Astig (R874) and the FOCUS control for
the best defined waveform.
Disconnect the test equipment from the instrument.
Adjust Trace Alignment
Position the trace to the center horizontal graticule
line.
ADJUST-The TRACE ROTA-I'ION control for opti-
mum alignment of the trace with the center horizontal
graticule line.
Adjust Geometry (R870)
Set:
CH 1 VOLTSIDIV 50 mV
A SECIDIV 0.1 ms
Connect 50-JLS time markers from the time-mark
generator via a 50-0 cable and a 50-0 termination
to the CH 1
OR
X input connector.
Adjust the Channel 1 POSITION control to position
the baseline part of the display below the bottom
horizontal graticule line.
Adjust the SECIDIV Variable control for 5 markers
per division.
ADJUST-Geom (R870) for minimum curvature of
the time markers at the left and right edges of the
graticule.
Set the Channel 1 lnput Coupling switch to GND.
ADJUST-Geom (R870) for minimum curvature of
the baseline trace when positioned at the top and
bottom horizontal graticule lines using the Channel 1
POSITION control.
Set the Channel 1 lnput Coupling switch to DC.
Repeat parts e through h for optimum compromise
between the vertical and horizontal displays.
Disconnect the test equipment from the instrument.
Check Scale Illumination
Rotate the SCALE ILLUM control between the maxi-
mum counterclockwise position and the maximum
clockwise position.
CHECK-The scale illumination lights are off in the
maximum counterclockwise position. The bright-
ness of the scale illumination lights increases as the
SCALE ILLUM control is rotated to the maximum
clockwise position.
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by ARTEK MEDL4
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